1. 450 GeV Initial Commissioning with Pilot Beam - Beam Instrumentation
LHCCWG
5th April 2006
Rhodri Jones (CERN – AB/BI)

2. Instrumentation – the essentials
From Chamonix 2006
Sector test & first turn
Screens, BPMs, fast BCT, BLMs
Circulating beams at 450 GeV
BPMs, DC BCT & lifetime (fast BCT) , BLMs
Tune, chromaticity & coupling
Emittance: wire scanners.
Snapback and Ramp
Continuous Tune, Chromaticity & Coupling
Orbit (+ feedback)
BLMs to beam interlock controller etc.
Continuous emittance monitoring: synchrotron light
LHCCWG, April Rhodri Jones (CERN - AB/BI)

3. BPM System at 450GeV
Already commissioned (injection & first 200 turns)
acquisition chain
asynchronous mode
most polarity errors found during threading & first turn measurements
Steps after RF capture
“time-in” the BPM system for bunch tagging
Set phase with respect to bunch for each monitor
Set turn clock with respect to end of dump gap for each monitor
is the pilot always in slot 1?
Requires BST
start orbit acquisition at 10Hz
Verify coherence of orbit, multi-turn and post mortem data
Estimate ~4hrs if all goes well!
LHCCWG, April Rhodri Jones (CERN - AB/BI)

4. BPM System at 450GeV Next Steps calibrate the BPM system
All monitors & orbit correctors - a la TI8
~30secs per COD (530 CODs per plane)
~9hrs for all
Accuracy will depend on accuracy of optics model!
Pre-requisite for orbit feedback
Finer calibration for interlock BPMs in LSS6 & BPMs at injection Pts.
Required to accurately set TCDQ etc.
First attempt at orbit feedback?
Required before we start to use collimators?
Controller tested without beam
Optimise closed loop gain (~1hr beam time)
LHCCWG, April Rhodri Jones (CERN - AB/BI)

5. BLM System at 450GeV Already Commissioned
Hardware functionality & detector availability
First Adjustment of Thresholds
Initially set as factor 3 below estimated quench level at 450GeV
Based on
simulations
lab heating test measurements (SM18)
possible sector test data
Thresholds adjusted either on a
Quench & learn basis if too high
Dump & learn basis if too low
Threshold change procedure under discussion in MPWG
At 450GeV fast loss damage level is factor 1000 above quench level
No risk of damaging components
LHCCWG, April Rhodri Jones (CERN - AB/BI)

6. BLM Threshold Level Estimation
LHCCWG, April Rhodri Jones (CERN - AB/BI)

7. BCT System Commissioning
Already commissioned
BCTFR (fast BCT) response to single pass (injection) and circulating non-captured beam
Circulating beam at 450GeV
First check of DCCT response
Cross calibration between the 2 DCCTs & 2 BCTFRs
Beam presence flag and beam safe flag for early running
Beam presence detected using simple comparator on BCTFR
Safe Beam flag derived 1Hz intensity measurements of BCTDC (software)
Commissioned at this stage
Fast Beam Loss Rate Monitoring
MPWG require measurement of loss of protons within a ms
BCTFR response will depend on % of bunch intensity lost
Loss of for 43 nominal bunches  7% change in bunch intensity (OK)
Loss of for 2808 nominal bunches  0.1% change (below noise limit)
NOT commissioned at this stage
LHCCWG, April Rhodri Jones (CERN - AB/BI)

8. Early LHC BCT System Performance
Measurement Mode
Beam type
Accuracy/
Resolution
Fast BCT
(BCTFR)
DC BCT
(BCTDC)
Injection
Pilot bunch
±20% / ±20%
±109
(OK)
N/A
Nominal bunch
±3% / ±1%
±3·109 / ±109
Circulating
Beam
(>200 turns)
±10% / ±10%
±0.5·109
1mA (on 10mA)
(resolution ~2-10mA)
±1% / ±1%
2mA (on 180mA)
(limit for short int time)
43 pilot bunches
2mA (on 390mA)
Lifetime
10% (10hrs/1min)
10%
(30hrs/10sec)
LHCCWG, April Rhodri Jones (CERN - AB/BI)

9. Tune, Chromaticity & Coupling
Day 1 with kicked beams and classical motion analysis
Commission MKQ
Base Band Tune (BBQ) system for tune & coupling
Optimisation of gains & time constants
Head-tail system for chromaticity
Verification of chromaticity with dp/p variation
Commission chirp excitation using the transverse damper
Allows faster rep rate if required
BBQ system + chirp generation
will replace BOSC as Standard Tune measurement for SPS in 2006
All hardware & analysis software should therefore be operational in the LHC as soon as we have beam
LHCCWG, April Rhodri Jones (CERN - AB/BI)

10. Tune, Chromaticity & Coupling
PLL tune tracking (US-LARP)
Also based on BBQ acquisition
Separate system from standard kicked tune system
Set-up in parallel to single kick
Requires dedicated kicker BQK (if installed) or Damper
Question: Do we go all out for tune and coupling feedbacks?
If so, then this is the time to commission them
Coupling control is critical for orbit & tune feedbacks
Spending some time here to commission these systems
early on may significantly reduce the time required for
ramp development
LHCCWG, April Rhodri Jones (CERN - AB/BI)

11. Coupling Feedback at RHIC (2006)
LHCCWG, April Rhodri Jones (CERN - AB/BI)

12. Tune & Coupling Feedback at RHIC (2006)
LHCCWG, April Rhodri Jones (CERN - AB/BI)

13. Feedback using the PLL tune system
Tune feedback requirements
Stable PLL tune measurement system
Knowledge of correction quad transfer functions
already known from initial tune corrections
Implementation of feedback controller
Coupling feedback requirements
Knowledge of skew quad transfer functions
Chromaticity feedback requirements
RF frequency modulation
All of these will require dedicated beam time for testing the control loop response and the final closing of the loop.
LHCCWG, April Rhodri Jones (CERN - AB/BI)

14. Measuring Beam Size at 450GeV
Wire Scanners (BWS)
Operational
Synchrotron light monitor (BSRT)
Requires undulator to be ON
Cross calibration with wirescanner
Requires “stable” beams
Ionisation profile monitor (BGI)
Verification of bump closure of BGI compensators
Should be negligible even at 450GeV
Requires pressure bump for pilot bunches if nominal vacuum
LHCCWG, April Rhodri Jones (CERN - AB/BI)

15. Abort Gap Monitor (BSRA)
Requirement – detect at 10% of quench level
At 450GeV : detection of 4×109 charges/100ns within 100 ms
At 7TeV : detection of 6×106 charges/100ns within 100 ms
Protons
Gated photomultiplier will look at synchrotron light using same light source as synchrotron light monitor
Either gated over entire 3ms abort gap or in 30, 100ns time slots
Single pilot bunch will allow verification and calibration of photon production to proton number
Estimate ~300 photons / 100ns / turn at 450Gev
May require tunnel intervention to change light splitting ratio between BSRT and BSRA
Should be commissioned before we increase intensity
Check of threshold
Check of timing
Check of interlock (BIC?)
LHCCWG, April Rhodri Jones (CERN - AB/BI)